Subject: [mobile-ip] Question about sending BU to CN

From: "Krishna Kumar" <[email-masked]>
Date: Fri, 27 Sep 2002 15:44:09 -0700

Hi all,

Regarding Section 11.6.2, the following para is giving me some problems :

      "When a mobile node sends a Binding Update to its home agent
      to register a new primary care-of address (as described in
      Section 11.6.1), the mobile node SHOULD also start a return
      routability procedure to each other node for which an entry exists
       in the mobile node's Binding Update List, as detailed below.  Upon
      successful return routability procedure and after receiving a
      successful Binding Acknowledgement from the Home Agent, a Binding
      Update message is sent to all other nodes.  Thus, other relevant
      nodes are generally kept updated about the mobile node's binding and
      can send packets directly to the mobile node using the mobile node's
      current care-of address."

Shouldn't the RR be started only after the BA is received from the HA ?
When the
MN moved from FN1 (Foreign Network 1) to FN2 and sent the BU to it's HA, it
has
entries in it's BUL for CN's it was interracting with while it was in FN1.
So if it sent the
BU and started the RR before receiving the BA (or atleast before BA was
sent by
the HA), it is possible that the RR packets meant for the MN at FN2 would
get
routed to it's COA at FN1. this means that the HoT message may not
propagate
properly to the MN's new COA.

Is this problem correct ? If so, the text should change to something like :

      "When a mobile node receives the Binding Acknowledgement from
      it's Home Agent, ..... Upon successful return routability procedure,
a Binding
      Update message is sent to all other nodes. ....... "

Thanks,

- KK

---

From: Vijay Devarapalli <[email-masked]>
Date: Fri, 27 Sep 2002 17:55:47 -0700

> properly to the MN's new COA.

I understand your concern. you dont want to start HoTi/HoT exchange
before you can make sure that the HA has your new CoA in its BCE.
you are concerned that the HoT would go to the wrong CoA. actually
this wont happen. the HoTi itself gets dropped. the HoT would fail
the CoA check in the reverse tunneled packet. if the CoA on the
reverse tunneled HoTi does not match the contents of the BCE, the
HA drops the HoTi.

if the home cookies is reused and is valid when the MN moves, this
problem can be avoided.

in general, I think it is a bad idea to delay RR procedure till the
BAck comes back. the MN should do it as soon as possible (now that
previous router notification has been removed).

regards
Vijay